A separation method using a membrane has lots of advantages over the method based on heating or phase-changing. Among the advantages is high reliability of water treatment since the water purity required can be easily and stably satisfied by adjusting the size of the pores of a membrane. Furthermore, since the separation method using a membrane does not require a heating process, a membrane can be used with microorganism which is useful for separation process but may be adversely affected by heat.
Among the membrane employing separation methods is a method using a hollow fiber membrane module which comprises a bundle of hollow fiber membranes. Conventionally, the hollow fiber membrane module has been widely used in a micro-filtration field for producing axenic water, drinking water, super pure water, and so on. Recently, however, the application of the hollow fiber membrane module is being expanded to include sewage and waste water treatment, solid-liquid separation in a septic tank, removal of suspended solid (SS) from industrial wastewater, filtration of river, filtration of industrial water, and filtration of swimming pool water.
One kind of the hollow fiber membrane modules is a submerged-type hollow fiber membrane module which is submerged into a water tank filled with fluid to be treated. Negative pressure is applied to the inside of the hollow fiber membranes, whereby only fluid passes through the wall of each membrane and solid elements such as impurities and sludge are rejected and accumulate in the tank. When used for separation, the plural submerged-type hollow fiber membrane modules are installed in a frame structure. A submerged-type hollow fiber membrane module is advantageous in that the manufacturing cost is relatively low and that the installation and maintenance cost may be reduced since a facility for circulating fluid is not required.
FIG. 1 illustrates one example of a related art submerged-type hollow fiber membrane module.
In case of the related art submerged-type hollow fiber membrane module 100 shown in FIG. 1, a plurality of hollow fiber membranes 120 are arranged in a bundle between two headers 110. Both ends of the hollow fiber membrane 120 are respectively potted to confronting sides of the two headers 110 by an adhesive of polyurethane. In this case, a permeate collecting unit (not shown) is formed in each of the headers 110, wherein the permeate colleting unit is connected with open ends of the hollow fiber membrane 120 so as to collect permeate passing through the hollow fiber membrane 120.
Between the confronting sides of the two headers 110, there are two upper supporting members 131 and two lower supporting members 132 so as to stably maintain an interval between the two headers 110.
In the meantime, as shown in FIG. 2, a filtering apparatus using the submerged-type hollow fiber membrane module has a structure including a plurality of hollow fiber membrane modules 100a, 100b, 100c, and 100d packed into a frame structure (not shown), wherein the filtering apparatus performs a filtering process while being submerged into a liquid substrate containing impurities.
However, when the submerged-type hollow fiber membrane module is used to treat wastewater, the solids in the wastewater fouls the membranes causing their permeability to be declined as the water treatment is processed. Thus, while the water treatment is carried out by the hollow fiber membrane modules 100a, 100b, 100c, and 100d, an aeration process has to be performed for stably maintaining the high permeability of the membranes. In the aeration process, air is jetted from an aeration pipe (not shown) positioned under the hollow fiber membrane modules 100a, 100b, 100c, and 100d during the water treatment, thereby generating rising air bubbles. Thus, foreign materials are removed from the membrane surface owing to the rising air bubbles.
However, the respective hollow fiber membrane modules 100a, 100b, 100c, and 100d may be intensely shaken or vibrated due to the rising air bubbles from the aeration pipe for the aeration process of the filtering membrane. Furthermore, there is a high possibility that the hollow fiber membrane modules 100a, 100b, 100c, and 100d are damaged by their collision. In order to minimize the damage in the hollow fiber membrane modules 100a, 100b, 100c, and 100d, they have to be maintained for being in close contact with one another, fixedly.
If any one of the hollow fiber membrane modules 100a, 100b, 100c, and 100d has to be replaced or repaired due to the damage thereof, it is necessary to pull out the hollow fiber membrane module to be replaced or repaired from the filtering apparatus.
However, in the filtering apparatus of FIG. 2, the hollow fiber membrane modules 100a, 100b, 100c, and 100d are maintained for being in close contact with one another. In addition, each of headers 110a, 110b, 110c, and 110d in the hollow fiber membrane modules 100a, 100b, 100c, and 100d is provided with only flat surfaces. Thus, when trying to individually pull out the hollow fiber membrane module 100b or 100c, which is positioned in the center of the frame structure, among the hollow fiber membrane modules 100a, 100b, 100c, and 100d, a pulling force is hardly transmitted to the corresponding hollow fiber membrane module 100b or 100c without securing an enough space at both sides of the header 110b or 110c. Furthermore, a large-sized hollow fiber membrane module according to a recent trend requiring a large water-treatment capacity may cause more difficulty in individually pulling out each individual hollow fiber membrane module from the filtering apparatus.